Device for de-watering mud,sludge or fibre suspensions



Unite States Patent Inventor Tad (ilowacki,

Hembergav'aigen 3, 183 42 Tiiby, Sweden Appl. No. 833,388 Filed June 16. 1969 Patented Oct. 13, 1970 Priority June 26, 1968,

Sweden, 8,694/68 2 l0/337,38U Int. Cl 1304b 3/04 Field ofSearch 210/374.

[56] References Cited UNITED STATES PATENTS 2.043.662 6/1936 Howe 2lU/374 X 3,221.879 12/1965 lrving 21U/374X Primary Examiner-J. L. DeCesare Attorney-Burns. Doane, Benedict, Swecker and Mathis ABSTRACT: A de-watering device for mud, sludge or fibre suspensions having a feeder screw mounted for rotation in a perforated drum in which the feeder screw feeds the mass to be de-watered from an inlet opening to an annular outlet opening formed between an extension of the core of the feeder screw and the end portion of the cylindrical wall of said drum, and in which there are a plurality of tiltably pivoted flaps covering the outlet opening, each flap being individually biased so as to open individually against the bias under the influence of the pressure from the de-watered pulp.

Patented 03.13, 1970 12in Cinvmcm INVENTOR. hYflaM Patentefi ct. 13, 1970 Sheet TAD GIDWACKI fKM maasw Patented Oct, 13, 1970 Sheet TA [9 G LO WA (KI INVENTOR.

DEVICE FOR DE-WA'IERING MUD. SLEDGE OR FIBRE SUSPENSIONS The present invention relates to a device for de-watering mud, sludge or fibre suspensions, said device comprising a feeder screw. a drum surrounding said feeder screw. said drum being preferably provided with perforations. an inlet opening in one end of said drum and an annular outlet opening in the other end of said drum, said outlet opening being formed between a circular opening in the end wall portion ofthe drum and a flow regulator which is located on the extension of the core of said screw.

In known devices of that kind, the suspension supplied to the device is caught by the threads of the feeder screw and is fed forwards towards the annular outlet opening. During this movement, the material is compressed owing to the fact that the outlet opening is rather narrow and thereby water or other liquid is removed from the compressed material and is brought to flow away through the perforations of said drum. The remaining water content of the pulp, which is fed out through the outlet opening, is to a great degree determined by the size of the outlet opening.

It is known to make the size of the outlet opening variable, for example by arranging the generally conical flow regulator spring loaded in an axial direction, so that, when a tendency for. forming plugs or knots occurs in the outlet opening, the flow regulator is displaced outwards from the outlet opening whereby the outlet opening automatically will be greater. Therefore, the plug or knot will be fed out so that the pressure of the pulp at the outlet opening will be decreased. Thereafter, said flow regulator will be displaced towards the outlet opening, under the action of the spring force, to its original position.

It has also been suggested to make the drum and its end wall portion spring loaded in an axial direction and by such a device a similar operation is obtained as when the flow regulator is spring loaded.

It has been noticed, however, that in de-watering devices of the kind indicated it sometimes occurs a sudden increase of the feeding out ofa very wet pulp. In such instances, the automatical adjustment of the outlet opening fails to operate properly. This is depending on a knot or plug that is formed at the outlet opening and is broken through at one place, while at the other places of the outlet opening, the plug remains firm. The remaining parts of the plug maintain a high pressure between the flow regulator and the outer wall of the outlet opening, and therefore, the size of the outlet opening remains rather great. Under such conditions, an incompletely dewatered pulp may flow out in great quantities at such parts of the outlet opening where the plug has been broken through and where parts of said plug have been fed out. While said conditions prevail, bigger and bigger portions of the plug will be removed by the wet pulp which is streaming out, and finally, the whole plug will be removed. Until then, however, great quantities of incompletely de-watered pulp have been fed out.

A screw press is also known in which the end wall portion of the drum where the annular outlet opening is formed, is divided in four parts, each part being spring loaded and displaceable radially outwards from an extension of the screw which extends through the outlet opening. In this device, each quarter of said wall portion can be displaced outwards individually. No great improvement regarding the uniform dewatering operation of the device has, however, been noticed by using said arrangement. Ifa plug is formed round the whole annular outlet opening, and a part of said plug later is broken through and fed out, this does not generally lead to that one of the parts of the wall portion is displaced inwards again and, therefore, great quantities of insufficiently de-watered pulp are fed out through the opening.

One object of the present invention is to provide a device for de-watering sludge, mud or fibre suspension in which the drawbacks of the hitherto known devices are avoided and which gives a uniformly de-watered pulp even if the mass supplied to the devicehas a great tendency for forming knots or plugs.

According to the present invention a device for de-watering mud, sludge or fibre suspension is provided. said device comprising a feeder screw. a drum surrounding said feeder screw and provided with perforations, an inlet opening at one end of the drum, and an annular outlet opening at the other end of the drum, said outlet opening being formed between a projecting cylindrical member which forms an extension of the core of the feeder screw and the edge of a circular opening in the end wall portion of said drum. and in which said end wall is divided into a plurality of parts, each part being individually resiliently biassed towards said cylindrical member. wherein each portion of said end wall has the shape of a trapezium and each such wall portion is tiltably pivoted with its longest parallel edge to a pivot axis which is located at a distance from the periphery of said cylindrical member which corresponds to the maximum obtainable radial width of said outlet opening and each wall portion has a tangential length which is substantially equal to its radial width.

By this arrangement an individual flexibility of each single pan of the annular end wall portion which defines the annular outlet opening will be obtained. Thereby, the size of the outlet opening at each individual place will be automatically adjusted according to the shape and pressure of the pulp which is fed out at this particular place. This means, that if a plug or knot has been formed and been broken through at one place, one or several wall portions will be pressed inwards at this place, and the pressure of the pulp at this particular place will increase again, so that the pulp is compressed and a satisfactory de-watering degree will be maintained. When the pressure has risen sufficiently, the whole plug will be fed out because of the flexibility of the whole wall portion. Thereafter, the size of the outfeed opening will decrease again and the operation will be restored to its normal condition.

According to a preferred embodiment of the invention the resilient pressure applied to each wall portion is obtained by a pneumatic cylinder and a piston in said cylinder, in a manner known per se.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which FIG. 1 illustrates a de-watering device according to the invention, as viewed from the side, in one of its operating conditrons.

FIG. 2 is the same device as in FIG. I in another operating condition.

FIG. 3 is the same device as viewed from the outlet end.

FIG. 4 is a section through the inlet opening of a de-watering device of a conventional construction.

FIG. 5 is a corresponding section of the device according to a modification of this invention.

In FIG. 1, a base plate of the de-watering device is designated 1. The device comprises a feeder screw 2 and a perforated drum 3 surrounding said feeder screw. The drum 3 is provided with an inlet opening 4, which is directed radially into the drum. The fluid which is pressed from the treated suspension is removed through the perforations of the drum and is allowed to flow away through a channel 5 or the like. At its front end, the drum 3 has an annular end wall which according to the shown embodiment of the invention, is divided into twelve trapezium shaped wall portions (see FIG. 3). Each wall portion 6 is rotatably hinged by hinge means 7 at the longest parallel edge of said wall portion. Each wall portion 6 is actuated by a lever 8, one end of said lever being fastened to the wall portion and the other being linked to a piston rod 9. The piston rod 9 carries a piston 10 which is slidable in an air pressure cylinder 11. The pressure in the cylinder 11 behind the piston is sufficiently great to keep each wall portion 6 substantially to rest on the periphery of a flow regulator I2 which is integral with or constitutes an extension of the core of the screw 2.

The screw 2 is connected to or forms a part of a shaft 13 which is pivoted in a front bearing [5 and in a rear bearing 15a (schematically illustrated in FlG. 1). In the position illustrated in FIG. 1, the annular outlet opening 14 between the wall portions 6 and the flow regulator 12 is closed or very small. When mud or sludge is supplied to the inlet opening 4 and transported forward towards the outlet opening l4. it will be compressed by the threads of the screw 2, whereby liquid is removed through the perforation of the drum 3 and allowed to flow away through the channel 5. The de-watercd pulp is fed out through the outlet opening 14 and thereby the wall portions 6 will be tilted outwards towards the position shown in FIG. 2, against the action of the resilient pressure from the air cylinders 11. Before the wall portions have been entirely tilted outwards to parallelity with the axial direction of the screw 2. there will be a star-shaped outfccd opening formed.

If there is a tendency to form a plug or knot at the outfeed opening, the wall portions 6 will be opened more to let such plug pass. If, however, the plug is broken through in one place, one or several wall portions, which are located at that particular place, will be closed independent of the other wall portions, so that the outlet opening at that particular place will be decreased. Because of that, a pressure is again formed behind the flow regulator 12, so that the de-watering procedure will continue undisturbed.

After some time the pressure has risen to a value which is sufficient to feed out the whole plug, and thereafter the operation of the device will be restored to its normal condition.

The screw 12 may be driven from a stud H6 at the right end of the screw, said stud being connected to a motor or some other machine (not shown).

In a tie-watering device of the kind indicated the operation will sometimes be disturbed by forming of knots in the inlet opening. in FlG. 4, there is a cross section through the inlet opening and the feeder screw ofa de-watcring device of a conventional type and in FIG. is the corresponding cross section of a preferred embodiment of the device according to the invention illustrated. in the conventional device (see FIG. 4) it frequently happens that the sludge or mud which is supplied to the inlet opening 4 is baked together to a plug or knot i7, which prevents the substance from being fed down into the threads of the screw and therefore the screw has a tendency to run unloaded. in FIG. 5, there is illustrated how a device according to the invention should be shaped in order to avoid said difficulty. In this device, the width of the inlet opening is increased at the inlet side of the screw so that a wedgeshaped pocket 18 is formed between the screw threads and the adjacent wall of the inlet opening 4. in this device, the material which is supplied to the inlet opening is forced down into the pocket it because of the movement of the screw. The materia'l will be pressed harder and harder between the wall portion of the inlet opening 4 and the screw and into the threads of the screw and will be fed forwards by the screw as intended.

Although the invention has been described in connection with some definite embodiments of the same, other embodiments can be had within the scope of the appended claims.

l claim:

. 1. in a de-watering device comprising:

a feeder screw having a projecting cylindrical member constituting an extension of the core thereof;

a perforated drum surrounding said feeder screw. said drum having an inlet opening at one end thereof, the other end of the drum and said cylindrical member defining an annular outlet opening;

flow regulator means for controlling the size of the outlet opening, said flow regulator including a plurality of trapa-' zoid-shaped wall portions each mounted onsaid drum for pivotal movement about its longest parallel edge; and

means for resiliently biasing each of said wall portions towards said cylindrical member to close said inlet opening.

2. A device according to claim 1 wherein said biasing means includes a plurality of pneumatic devices carried by said drum, each of said devices comprising an air pressure cylinder having a piston connected at the free end thereof to one of said wall portions.

3. A device according to claim 2 wherein said inlet opening comprises a wedge-shaped pocket formed between that side of the feeder screw moving away from the inlet opening and the adjacent wall portion of the inlet opening to force material to be de-watered down into the pocket thus formed and into the thread of said feeder screw.

4. A device according to claim 1 wherein said feeder screw includes a continuous thread having multiple turns about said core.

5. A device according to claim 4 wherein said feeder screw is substantially horizontal and wherein said inlet opening is directed radially into said drum.

6. A device according to claim 1 wherein said feeder screw is substantially horizontal and wherein said inlet opening is directed radially into said drum.

7. A device according to claim 6 wherein the radial width of each of said wall portions is substantially equal to the length of the longest parallel side thereof.

8. A device according to claim 7 wherein said biasing means includes a plurality of pneumatic devices carried by said drum, each of said devices comprising an air pressure cylinder having a piston connected at the free end thereof to one of said wall portions. 

